Apparatus



J. A. LAIRD Filed Feb. 11. 1942 1720 6373! L w 6rd FM f/fqs ANMAAAAA vvvvvvv Aug. 22, 1944.

ELECTRIC IGNITION SYSTEM AND nrmwus Patented Aug. 22, 1944 amc'rarc IGNITION SYSTEM AND armas rus John ABM Laird, Birmingham, England, assignor to Bendix Aviation Corporation, New- York, N. Y.

Application February 11, 1942, Serial No. 430,443 In Great Britain January 16, 1941 18 Claims.

This invention relates to electric-ignition apparatus for internal combustion engines,and has for its object to provide improved means for enabling sparks to be produced in rapid succession.

The invention comprises the combination of a current generating winding, a transformer having a primary winding connected in series with the generating winding and a secondary winding adapted to produce the required sparking voltages at the engine plugs, a make and break device adapted to short-circuit the generating winding, and means for dissipating the residual energy in each cycle.

In the accompanying sheet of explanatory diagrams, Figures 1-6 illustrate different modes of carrying the invention into effect. Referring to Figure 1, I employ any convenient current generating apparatus, such as generating winding a and magnetic means M for generating current impulses in the winding. I also employ any convenient transformer having primary and secondary windings b, c which are preferably closely coupled for example by a closed-iron magnetic circuit, such as a core 0. The primary winding b is connected in series with the generating winding a, and the secondary-winding c is adapted to produce the sparking voltage required at the engine plugs. In series with the generating winding is arranged any convenient make and break device 11 adapted to be operated by the engine. This device d is such that when closed it shortcircuits the generating winding a and when open it allows current to flow from the generating windingto theprimarywindingbofthetransformer. At any convenient position is arranged asscond and similarly operated make and break device e in series with one end of the transformer primarywinding b,and acrossthisdeviceisconnected a substantially non-inductive resistance 1. The usual condenser a is connected across the that make and break device at, and preferably another condenser h is connected acrom'the sec- -'ondmakeandbreakdeviceeandtheresistancej.

In each cycle of operations the mode of action is as follows: With both make and break devices 4,

rent flowing in the winding (1. Finally both make and break devices d, e, are closed in readiness for the next cycle.

As shown in Figure 1 the make and break device d is situated between the generating winding 41 and the second make and break device e, but this is not an essential condition as the first make and break device d may be situated between the second make and break device e and the transformer primary winding b as shown in Figure 2 which is otherwise similar to Figure 1.

In the modification shown in Figure 3 I dispense with the second make and break device above described and arrange a resistance i in In the further modification shown in Figure 4,.

in which the second make and break device e is retained, I use a condenser o in series with a resistance p, and connect them across the second make and break device, the residual energy stored in the condenser in each cycle being dissipated when the-second make and ,break device is closed preparatory to the next cycle.

The otherpartsofl'iguretaresimilartothose employed in the previously described examples.

In the modification shown in Figure 5 I employ a generating winding 4, a transformer b, c and a make and break device 1! as in the examples previously described, the transformer windings being preferably closely coupled. by. for example, a

. closed-iron magnetic circuit. The generating and primary windings a, b are interconnected by. a resistance is preferably one having little or no inductance." This resistance may be placed as shown between one pair of ends of the windings a. b, or it may be divided and placed between both ends. In anycaseitisinserieswithboth ofthese windings, and its amount is such that whilst not suflicient to reduce materially the amount of energy required to be transferred from the generating winding a to the transformer primary winding b is sufllcient to effect rapid dissipation of the residual energy in the system after a spark has been produced. The optimum value for the resistance k can easily be ascertained by experiment.

In addition to the make and break device I! which when closed short circuits the generating winding 0, and when open allows current to pass from the generating winding to the transformer primary winding 1: through the resistance 7:, I employ a second make and break device m which is also adapted to be operated by the engine, and which is arranged in parallel with the transformer primary winding, this second device being situated between the latter winding and the resistance. When open the device m allows current to pass to the primary winding b from the generating winding a, but when closed it provides an alternative path for the current such that little or no current then passes to the primary winding.

In each cycle of operations the mode of action is as follows: With the first make and break device d closed current is generated in the generatwinding a,'the other make and break device being open. At the appropriate instant the first make and break device it is opened causing current to flow from the generating winding a through the resistance is to the transformer primary winding 2) and a spark to be produced at the plug connected to the secondary winding c. After a very short time interval the second make and break device m is closed thereby providing an alternative path for the discharge and virtually isolating the transformer b, c. The residual energy is then rapidly dissipated in the resistance is. Prior to the next cycle the first make and break device d is re-closed and the other make and break device m re-opened, and then the cycle is repeated. If desired a condenser g may be combined with one or each of the make and break devices d, m to minimise sparking at its H contact.

In a further modification I provide a third make and break device n connected in parallel with resistance is in the embodiment of Fig. 5, as shown in broken lines in Figure 6, for shortcircuiting the resistance k while current is being discharged through the primary winding b of the transformer. This additional device n may be incorporated with the second makeand break device m above described,.or it may be a separate device suitably co-ordinated with the other make and break devices d, m.

By this invention I am able to produce high tension sparks in very rapid succession and thereby satisfy the requirements of engines in which this condition is necessary.

Although the values of the various elements of the above-described circuits in electrical units may vary in ignition systems for different engines, it has been found that in suitable ignition systems for present-day engines the generating winding a may have an inductance of approximately 4 milli-henries and a resistance of approximately .1 ohm, while the coil b may have an inductance of approximately 5 milli-henries and a resistance of approximately .5 ohm. It will be clear, of course, that the resistance i of Fig. 3, which may be approximately 20 ohms, may be incorporated in coil 1;, if desired, said resistance being shown as a separate unit for the purpose of illustration only. The resistance 1 of Figs. 1 and 2 may also have a value of approximately 20 ohms, while the resistance p and k of Figs. 4 and 5 are preferably approximately 5 ohms and 10 ohms, respectively. In each instance the value of the resistance depends to a large extent on the amount of residual energy in the primary circuit to be dissipated and the time which is available for dissipating the same. With respect to the various condensers in the circuits shown, condensers u and 0 may have a value of approximately .3 micro-farad, while condensers h and 1 may have values of .1 micro-farad and 2 microiarad, respectively.

Having thus described'my invention what I claim as new and desire to secure by Letters Patent is:

1. In an electric-ignition apparatus for internal combustion engines, an electric circuit comprising the combination of a current generating winding adapted to be energized by magnetic means, a transformer having a primary winding connected in series with the generating winding and a secondary winding adapted to produce the required sparking voltages at the engine plugs, the saidprimary winding being in one of two parallel connected branches of said circuit, a make and break device in the other of said branches adapted to short-circuit the generating winding, and means including a resistance connected in series with said primary winding for dissipating the residual energy in said circuit after each spark at the engine plugs.

2. Electric-ignition apparatus as claimed in claim 1, in which the primary and secondary windings of the transformer are closely coupled by a closed-iron magnetic circuit.

3. Electric-ignition apparatus as claimed in claim 1 and having a second make and break device arranged in series with the transformer primary winding and in shunt with the resistance.

4. Electric-ignition apparatus as claimed in claim 1 and having a second make and break device arranged in series with the transformer primary winding, and a condenser in series with the resistance and connected across the second make and. break device.

5. Electric-ignition apparatus as claimed in claim 1 and having a second make and break device arranged in series with the transformer primary winding, the resistance being connected in a branch of the circuit in shunt with the second make and break device and the first and second make and break devices being in separate parallel connected branches of the circuit.

6. Electric-ignition apparatus as claimed in claim 1 and having a second make and break device arranged in series with the transformer primary winding, the resistance being connected in a branch of the circuit in shunt with the second make and break device and the first make and break device being connected in series with the second make and break device and in parallel with the transformer primary winding.

7. Electric-ignition apparatus as claimed in claim 1 and having a second make and break device arranged in series with the transformer primary winding, and a condenser in series with the resistance and connected therewith across the second make and break device, the first make and break device being connected in series with the second make and break device and the generating winding.

3. Electric-ignition apparatus as claimed in claim 1 and having a second make and break device arranged in series with the transformer primary winding, and a condenser in series with the resistance, the latter and said condenser being connected across the second make and break device, the first make and break device being connected in series with the second make and break device and in parallel with the transformer primary winding.

9. Electric-ignition apparatus as claimed in claim 1 and having the resistance arranged in series with the generating winding and the transformer primary winding.

10. Electric-ignition apparatus as claimed in claim 1 and having a resistance with a large positive temperature coefllcient arranged in series with the generating winding and the transformer primary winding.

11. Electric-ignition apparatus for internal combustion engines, comprising in an electrical circuit the combination of a current generating winding adapted to be energized by magnetic means, a transformer having a primary winding connected in series with the generating winding in one of a plurality of parallel connected branches of said circuit and a secondary winding adapted to produce the required sparking voltages at the engine plugs, a resistance in series with the generating and primary windings, and two make and break devices connected in two of the other of said parallel connected branches, one of the said devices being .adapted to short circuit the generating winding, and the other of the said devices being adapted when closed to provide an alternative current path, such that little or no current passes from the generating winding to the primary winding.

12. Electric-ignition apparatus as claimed in claim 11 and having a make and break device for shunting the resistance while current is bein discharged through the primary winding of the transformer.

13. Electric ignition apparatus for internal combustion engines, comprising the combination of a current-generating winding, magnetic means for generating current impulses in said winding, a transformer having a primary winding con nected in a circuit in series with the generating winding and a secondary winding adapted to produce the required sparking voltages at the engine spark plugs, a make and break device connected to said generating winding in parallelrelation with the said primary winding, said device being adapted to short circuit the generating winding, and means including a resistance for dissipating the residual energy in the circuit containing said primary winding when said make and break device is in open position.

- ance in said circuit in-series with said primary winding for dissipating residual energy in' said circuit while the make and break device is opened 15. an ignition apparatusfor the ignition system of an internal combustion engine, an

aasaevo electrical circuit comprising the combination of a current-generating winding adapted to be energized by magnetic means, a transformer having a primary winding adapted to produce the required sparking voltages at the engine spark plugs, said primary winding being connected in one of two parallel connected branches Of said circuit, a make and break-device in the other of said branches adapted to be periodically opened, and means including a resistance in said one branch in series with said primary winding for dissipating the residual energy in said circuit after each spark at the engine spark plugs.

16. In an ignition apparatus for the ignition system of an internal combustion engine, an electrical circuit comprising the combination of a current-generating winding adapted to be energized by magnetic means, a transformer having a primary winding connected in series with the generating winding and a secondary winding adapted to produce the required sparking voltages at the engine spark plugs, said primary winding being connected in one of a plurality of parallel connected branches of said circuit, a make and break device in another of said branches adapted to be periodically opened, and means including a resistance in said circuit in series with said primary winding for dissipating the residual energy in said circuit after each spark at the engine spark plugs.

1'7. In an ignition system for an internal combustion engine an electrical circuit comprising a generating winding, magnetic means for inducing alternating current in said winding, a transformer having a primary winding in one branch of said circuit, a make-and break device in a second branch of said circuit, said branches being congenerating winding, magnetic means for induc-' ing alternating current in said winding, a primary winding in one branch of said circuit, a make and break device in a second branch of said circuit, said branches being connected to said generating winding in parallel relation with each other and said device being adapted to be periodiv cally opened when the current flow therethrough approaches a maximum, and means including a second make and break device connected in series with said primary winding. and a resistance con.- nected in parallel with said second make and break device for dissipating residual energy in said circuit when both of said make and break devices are open.

JOHN ANDREW LAIRD: 

